Aphton Corporation Presents at ASCO the Results of a Study Determining the Immune Response to GD17 Immunogen as a Predictor for Survival in Colorectal, Gastric and Pancreatic Cancers.

Business Editors/Health/Medical Writers

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MIAMI--(BUSINESS WIRE)--June 7, 2004

Aphton Corporation (Nasdaq: APHT) announced today results of a study establishing the immune response to G17DT immunogen as a predictor of survival in patients with colorectal, gastric and pancreatic cancers. Paul Broome, MB., Ch.B., FFPM, Aphton's Vice president and Medical Director, Global Clinical Trials and Regulatory Affairs announced the results, during the "Gastrointestinal (Noncolorectal) Cancer" poster sessions at the American Society of Clinical Oncology (ASCO) annual meeting in New Orleans. The title of the presentation is "Immune response to Gastrin-17 as an independent covariate for survival in colorectal, gastric and pancreatic cancers."

G17DT is a cancer vaccine that stimulates the immune system to develop antibodies to the hormone gastrin17 (G17). Inhibiting gastrin inhibits cancer cell growth, proliferation and metastasis, leading to cell death. Recent results have shown that survival is prolonged in subjects who develop antibodies to G17 (G17 responders). Data was analyzed from three clinical trials in three different gastrointestinal cancers to assess the predictive ability of typical baseline parameters with regards to anti-G17 immune response and to demonstrate that anti-G17 immune response is a significant predictor for survival that is independent of the covariates identified. The covariates included demographics, baseline disease stage, baseline Karnofsky performance status (KPS) and laboratory values. Results indicated that subjects with advanced colorectal, gastric or pancreatic cancers that generated antibodies to G17, following administration of G17DT, had significantly prolonged survival compared to those who did not. This effect was independent of other covariates analyzed.

About the study:

Patients were evaluated from three multinational studies:

1. Study CC6: An open-label, multicenter, multinational study; designed to evaluate the effects of G17DT in combination with irinotecan in 161 patients with metastatic colorectal carcinoma refractory to previous irinotecan-based chemotherapy.

2. Study GC4: An open-label, multicenter, multinational study; designed to evaluate the effects of G17DT in combination with CDDP and 5-FU in 103 chemotherapy naive patients with metastatic or locally recurrent gastric or gastroesophageal cancer.

3. Study PC6: A randomized, placebo-controlled, double-blind, multinational study; designed to evaluate G17DT as a monotherapy in 154 chemotherapy naive patients with Stage II-IV pancreatic cancer unsuitable for tumor resection.

Patients were followed from date of enrollment to death. An anti-G17 immune responder was defined as a subject with either an anti-G17titer greater than or equal to1.2 ELISA units during the 12 weeks from the first G17DT administration (if the baseline anti-G17 titer was below the limit of quantification (BLQ)) or an anti-G17 titer of at least 1 ELISA unit increased from the baseline titer during the 12 weeks from the first G17DT administration (if the baseline anti-G17 titer was above BLQ).

The following results were presented at ASCO from the study:

-- Median survival in the subset of patients who demonstrated an

anti-G17 immune response was consistently longer than the

median survival of patients who did not demonstrate such a

response. In the CC6 study, overall median survival (MS) was

229 days; MS of anti-G17 immune responders was 274 days vs.

169 days for non-responders (p is less than 0.001, log-rank).

In the GC4 study, overall MS was 271 days; MS of anti-G17

immune responders was 303 days vs. 146 days for non-responders

(p=0.0082, log-rank). In the PC6 study, overall MS was 150

days; MS of anti-G17 immune responders was 176 days vs. 63

days for non-responders and 83 days for the placebo group

(p=0.003, log-rank). Prospective identification of the

patients who will demonstrate an anti-G17 antibody response is

not possible; none of the other various possible covariates

tested demonstrated a good predictive ability across the

various types of cancer tested.The correlation between immune

response and survival remained highly statistically

significant even after adjusting for other covariates. This is

exemplified by prolonged survival of responders versus

non-responders even in patients with the same baseline

characteristics

About G17DT

Anti-Gastrin 17 (G17DT), targets the hormone gastrin 17 to treat gastrointestinal cancers, including pancreatic, gastric, esophageal and colorectal cancer. Aphton's anti-gastrin targeted immunotherapy induces patients to produce antibodies that bind and neutralize the hormones gastrin 17 and gly-gastrin (a pro-gastrin), which are known to be involved in tumor progression in gastrointestinal (GI) cancers.

Gastrin is a key hormone in the embryological development of the gastrointestinal (GI) system. Post embryological development, most of the gastrin and gastrin receptor genes throughout the GI system are shut down. Significantly, gastrin genes are activated once again in precancerous cells and polyps and in cancer cells early in the development of its cancer. Gastrin secretion and the expression of gastrin receptors increases as the cancer progresses. Gastrin works by signaling through its receptor, the gastrin receptor (CCK-2/Gastrin-R).

In normal adult tissue, gastrin is only produced in the antrum region of the stomach and its receptor is produced only on its target cells found in the normal stomach (Parietal and ECL cells). Normally, gastrin is secreted by cells in the stomach, primarily after eating and is responsible for producing approximately 90% of the body's stomach acid.

In cancer cells, gastrin acts to signal growth and proliferation, conferring a growth advantage on them. Gastrin expression and the appearance of gastrin receptors have been associated with increasing malignant characteristics of GI tumors and with poorer prognostic outcomes. Specifically, gastrin is known to be in involved in the progression of colorectal, stomach, liver and pancreatic cancers.

Recent findings have shown that inhibiting gastrin inhibits cell growth, proliferation and metastasis, leading to programmed cell death (apoptosis). This tilts the balance, from cell growth, to cell suicide. Gastrin also stimulates the secretion and expression of other important growth factors and receptors within and on the surfaces of the cancer cells involved in tumor growth. Hence, inhibiting gastrin inhibits all of the foregoing factors that contribute to tumor growth and spread, resulting in tumor cell death. Aphton's anti-gastrin targeted immunotherapy adds a biological dimension to the treatment of gastrointestinal cancers. Gly-gastrin is also made by the tumors and like gastrin, is involved in the growth stimulation of the cancers.

About Aphton Corporation

Aphton Corporation is a biopharmaceutical company developing products using its innovative targeted immunotherapy technology for neutralizing hormones that participate in gastrointestinal system and reproductive system cancer and non-cancer diseases. Aphton has strategic alliances with Aventis Pasteur for treating gastrointestinal system and other cancers with G17DT in North America and Europe; GlaxoSmithKline for reproductive system cancer and non-cancer diseases worldwide.

This press release includes forward looking statements, including statements 1) the Company's belief that the results from this trial demonstrate that G17DT provides a safe, effective alternative for patients with pancreatic cancer; 2) the Company's belief that the data from this clinical trial supports initiation of worldwide registration of G17DT; and 3) the Company's belief that its anti-gastrin targeted immunotherapy approach has the potential to extend patient survival without adding toxicity. These forward-looking statements may be affected by the risks and uncertainties inherent in the drug development process and in the Company's business. This information is qualified in its entirety by cautionary statements and risk factor disclosure contained in the Company's Securities and Exchange Commission filings, including the Company's report on Form 10-K filed with the Commission on March 31, 2003. The Company wishes to caution readers that certain important factors may have affected and could in the future affect the Company's beliefs and expectations and could cause the actual results to differ materially from those expressed in any forward-looking statement made by or on behalf of the Company. These risk factors include, but are not limited to, (1) any modifications to the data arising in connection with preparing the registration of G17DT; (2) our ability to obtain regulatory approval for G17DT or produce G17DT in commercial quantities and gain commercial acceptance, (3) our ability to fund the registration and commercialization of G17DT; (4) intellectual property risks, (5) the impact of competitive products and pricing, and (6) changing economic conditions. The Company undertakes no obligation to update forward-looking statements to reflect events or circumstances after the date hereof.